The present invention relates to a piston ring, and particularly to an oil scraping ring of axially low structural height which is composed of an expander spring, made of a band-type or wire material, and at least one lamina resting, at least in part, on a plurality of radially extending resilient tongues of the expander spring and being supported radially by legs of the resilient tongues which are bent in an approximately axial orientation.
German Pat. No. 1,087,855 discloses a tangentially, axially and radially resilient wire clamping spring for an oil scraping ring in which the spring coacts with two laminae. To radially and axially clamp the individual laminae, separate inherently resilient turn portions of the expander spring are arranged such that adjacent turn portions alternately rest against one or the other lamina. The major portion of the expander spring, and consequently also its bending region, is disposed axially between the two laminae so that a relatively large axial structure results which does not meet requirements of present-day oil scraping rings. Moreover, it is relatively difficult, and thus quite expensive, to produce such wound expander springs.
Another expander spring for a piston ring is disclosed in U.S. Pat. No. 3,627,333. The spring employed is made of a band-type material and, when seen in the circumferential direction, is provided with alternating slots emanating from both inner and outer circumferential edge faces. In the region of the outer circumferential edge face of the expander spring there are provided alternating, approximately axially bent legs which each serve to radially support one lamina. The resilient, radially extending tongues here serve as support faces for the two laminae. In this spring, the bending region is comprised merely of the bent legs while the actual spring region is disposed exclusively between the two laminae. Very short lever arms are realized with this structural design of the spring, which results in a hard spring characteristic. In operation, there is a continuous relative movement between spring and lamina. The resulting wear between spring and lamina leads to a greater drop in tangential force in the case of a hard spring characteristic than with a softer spring characteristic.